The present invention relates to a method and apparatus for manufacturing a synthetic resin hollow member incorporating an intermediate element therein, for example, a synthetic resin-made strainer having a filter incorporated therein, and to such a synthetic resin hollow member.
Conventionally, when manufacturing such a synthetic resin hollow item incorporating an intermediate element therein, for example, a synthetic resin-made strainer having a filter incorporated therein, one generally known method which would be commonly considered is such that with a pair of synthetic resin-made half bodies previously molded which constitute a pair of shells of the hollow member, a separately manufactured intermediate element is disposed between the two half bodies, the two half bodies being then brought into abutment against each other and bonded together through application of adhesive to the abutment surface or by thermally melting the abutted portions, whereby a finished hollow member incorporating the intermediate element is obtained.
In this connection, it is also known to join the half bodies by filling a melted resin mass into an interior resin passage or outer peripheral resin passage formed along peripheral edge of the abutting portions. It is also known to carry out such melted resin loading into the resin passage by utilizing a molding die in which separate half bodies are molded, when the separate half bodies are joined together in such a way as aforesaid.
By employing such a method, it is possible to more stably ensure high strength of bond between the so joined half bodies and good sealing performance of the butt-joined portion as compared to the prior art practice in which such joining is carried out by adhesion or thermal melting.
Further, in Japanese Patent Application Laid-Open No. 7-217755, for example, there is disclosed a method utilizing the so-called “die slide injection (DSI) method” wherein a die assembly including a pair of dies is used such that one of the dies has a male molding portion and a female molding portion for molding one separate half body and the other die has a female molding portion and a male molding portion provided in opposed relation to the molding portions of the one die, and wherein after separate half bodies are simultaneously molded by using the die assembly (first injection), die opening is carried out once for insertion of a separately made intermediate element into one of the half bodies and one of the dies is caused to slide relative to the other die so that separate half bodies left in respective female molding portions are brought into abutment with each other before die clamping, with melted resin being injected onto peripheral edges of the abutting portions (second injection) to join the two half bodies together.
According to this DSI method, productivity can be considerably enhanced over the conventional method in which molding of separate half bodies and abutting/joining of the half bodies are carried out at separate stages.
An arrangement which can further enhance production efficiency in the manufacturing of synthetic resin hollow members is disclosed in, for example, Japanese Patent Publication No. 7-4830 which teaches a rotary injection molding die construction. It dose not intend to consider of manufacturing synthetic resin hollow members incorporating an intermediate element therein, but, the above mentioned die construction is basically a combination of molding dies adapted to be opened and closed relative to each other such that one of the molding dies is rotatable relative to the other die over a predetermined angular range, each die having a molding section consisting of at least one male molding portion and two female molding portions in a repetitive sequence of male/female/female in the direction of rotation for each rotational run over the predetermined angular range. In this conjunction, there is also disclosed a rotary injection molding method (so-called die rotary injection (DRI) method) wherein by using such a molding die assembly, molding separate half bodies and joining a pair of abutted half bodies are carried out during each cycle of rotational (e.g., forward-reverse) movement so that a finished product can be obtained for each cycle of rotational movement.
While, as stated above, productivity can be increased by utilizing the die slide injection (DSI) over the conventional practice in which the molding of half bodies and the abutting and joining the half bodies are carried out in entirely different stages, it has been still necessary that the intermediate element be manufactured separately from the half bodies and be manually inserted in place at the time of die opening midway during molding operation.
This involves a problem that a stage for manufacturing an intermediate element structure must be provided separately from the stage for abutting and joining the half bodies together, and also, it means that the need for troublesome manual operation cannot be eliminated.
Therefore, it is a primary object of the present invention to provide a method and apparatus for manufacturing a synthetic resin-made hollow member incorporating an intermediate element which enable operations of molding half bodies, abutting and joining the half bodies together, and molding an intermediate element in a series of steps, and which eliminate the necessity of such a manual work as may otherwise be required in incorporating the intermediate element into the half bodies, and an synthetic resin-made hollow member produced by employing the method and apparatus.